PayPal API Http 调用问题答案

【问题标题】：Problems with PayPal API Http callPayPal API Http 调用问题
【发布时间】：2016-04-30 08:51:33
【问题描述】：

我已经集成了一个选项，供用户通过 PayPal 在我正在创建的网上商店中进行在线购物。当我开始收到此错误时，问题突然出现：

You must write ContentLength bytes to the request stream before calling [Begin]GetResponse.

Http调用的代码如下：

   public string HttpCall(string NvpRequest)
        {
            string url = pEndPointURL;

            string strPost = NvpRequest + "&" + buildCredentialsNVPString();
            strPost = strPost + "&BUTTONSOURCE=" + HttpUtility.UrlEncode(BNCode);

            HttpWebRequest objRequest = (HttpWebRequest)WebRequest.Create(url);
            objRequest.Timeout = Timeout;
            objRequest.Method = "POST";
            objRequest.ContentLength = strPost.Length;

            try
            {
                using (StreamWriter myWriter = new StreamWriter(objRequest.GetRequestStream()))
                {
                    myWriter.Write(strPost.ToString());
                }
            }
            catch (Exception e)
            {

            }

            //Retrieve the Response returned from the NVP API call to PayPal. 
            HttpWebResponse objResponse = (HttpWebResponse)objRequest.GetResponse(); // this is the line where the exception occurs...
            string result;
            using (StreamReader sr = new StreamReader(objResponse.GetResponseStream()))
            {
                result = sr.ReadToEnd();
            }

            return result;
        }

有人可以帮我解决这个问题吗？一天前它工作得很好，现在它给了我这个错误？

【问题讨论】：

标签： c# asp.net paypal httpwebrequest httpwebresponse

【解决方案1】：

在浪费了几个小时之后，结果证明是 Tls 协议版本。

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

【讨论】：

【解决方案2】：

好的，如果有人感兴趣，我可以通过在创建 Web 请求之前添加以下行来修复错误（我可以通过像这样进入 Tls12 来修复它）：

`ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12`;

干杯:-)

编辑试试这个：

 public string HttpCall(string NvpRequest)
    {
        string url = pEndPointURL;

        string strPost = NvpRequest + "&" + buildCredentialsNVPString();
        strPost = strPost + "&BUTTONSOURCE=" + HttpUtility.UrlEncode(BNCode);
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
        // Try using Tls11 if it doesnt works for you with Tls
        HttpWebRequest objRequest = (HttpWebRequest)WebRequest.Create(url);
        objRequest.Timeout = Timeout;
        objRequest.Method = WebRequestMethods.Http.Post;
        objRequest.ContentLength = strPost.Length;
        try
        {

            using (StreamWriter myWriter = new StreamWriter(objRequest.GetRequestStream()))
            {
                myWriter.Write(strPost.ToString());
            }
        }
        catch (Exception e)
        {

        }

        //Retrieve the Response returned from the NVP API call to PayPal. 
        HttpWebResponse objResponse = (HttpWebResponse)objRequest.GetResponse();
        string result;
        using (StreamReader sr = new StreamReader(objResponse.GetResponseStream()))
        {
            result = sr.ReadToEnd();
        }

        return result;
    }

【讨论】：

我也面临 .net 4.0 的相同问题。即使在我添加了 ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;我面临同样的问题。你能帮忙吗？ 4.0中没有Tls12
我试图实现你的代码，但它给出了同样的错误。
我的问题与所提到的不同，但您的修复对我有用。在我的情况下，PayPal 请求在本地机器上工作正常，但在生产服务器上不工作。

【解决方案3】：

public string HttpCall(string NvpRequest) //CallNvpServer
{
    string url = pendpointurl;

    //To Add the credentials from the profile
    string strPost = NvpRequest + "&" + buildCredentialsNVPString();
    strPost = strPost + "&BUTTONSOURCE=" + HttpUtility.UrlEncode( BNCode );

    HttpWebRequest objRequest = (HttpWebRequest)WebRequest.Create(url);
    objRequest.Timeout = Timeout;
    objRequest.Method = "POST";
    objRequest.ContentLength = strPost.Length;

    try
    {
        using (StreamWriter myWriter = new StreamWriter(objRequest.GetRequestStream()))
        {
            myWriter.Write(strPost);
        }
    }
    catch (Exception e)
    {
        /*
        if (log.IsFatalEnabled)
        {
            log.Fatal(e.Message, this);
        }*/
    }

    //Retrieve the Response returned from the NVP API call to PayPal


    HttpWebResponse objResponse = (HttpWebResponse)objRequest.GetResponse();
    string result;
    using (StreamReader sr = new StreamReader(objResponse.GetResponseStream()))
    {
        result = sr.ReadToEnd();
    }

    //Logging the response of the transaction
    /* if (log.IsInfoEnabled)
     {
         log.Info("Result :" +
                   " Elapsed Time : " + (DateTime.Now - startDate).Milliseconds + " ms" +
                  result);
     }
     */
    return result;
}

【讨论】：

嗨，我已经更新了我的答案，复制并粘贴我的代码，如果它适合你试试看。